WAEC 2013 Biology · Question 8

Which of the following statements is not correct about the mammalian heart?

Options

A.Oxygenated blood enters the left auricle from the pilmonary vein
B.the walls of the ventricle are thicker than those of the auricle
C.blood passes from of blood into the right ventricle to the left auricle through the aorta
D.the tricuspid valve prevents the back flow of blood into the right auricle

Answer: C. blood passes from of blood into the right ventricle to the left auricle through the aorta

Explanation written with AI and checked against the answer key

Analyze the question: You are asked to find the statement that is NOT correct about the mammalian heart. So three options are true, and one is false.

Concept review: The mammalian heart has four chambers (two auricles/atria and two ventricles) and a double circulation:

Right side: receives deoxygenated blood from the body via the vena cava (into the right auricle), then passes it to the right ventricle, which pumps it to the lungs via the pulmonary artery.
Left side: receives oxygenated blood from the lungs via the pulmonary vein (into the left auricle), then passes it to the left ventricle, which pumps it to the whole body via the aorta.
The tricuspid valve lies between the right auricle and right ventricle. The bicuspid (mitral) valve lies between the left auricle and left ventricle.

Check each option:

A. Oxygenated blood enters the left auricle from the pulmonary vein. TRUE. This is exactly the path of blood returning from the lungs.
B. The walls of the ventricle are thicker than those of the auricle. TRUE. Ventricles pump blood out of the heart over longer distances, so they need stronger, more muscular walls. The left ventricle is the thickest.
C. Blood passes from the right ventricle to the left auricle through the aorta. FALSE. Blood from the right ventricle goes to the lungs through the pulmonary artery, not the aorta. The aorta leaves the left ventricle. Also, there is no direct passage from the right ventricle to the left auricle, because the septum separates the two sides of the heart.
D. The tricuspid valve prevents backflow of blood into the right auricle. TRUE. It closes when the right ventricle contracts.

Tip: Remember the route: Body → vena cava → right auricle → (tricuspid) → right ventricle → pulmonary artery → lungs → pulmonary vein → left auricle → (bicuspid) → left ventricle → aorta → body. Also remember that the aorta always comes from the left ventricle. If an option mixes up the sides or vessels, it's likely the false one.

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